1. Field of the Invention
The invention relates generally to the field of photography, and particularly to a film cassette containing a film roll. More specifically, the invention relates to a film cassette wherein a leading end of the film roll can easily be advanced from within the film cassette to the outside of the cassette.
2. Description of the Prior Art
In the standard 35 mm film manufacturers' cassette, such as manufactured by Eastman Kodak Co. and Fuji Photo Film Co., Ltd., the filmstrip is wound on a flanged spool which is rotatably supported within a cylindrical shell. A leading end section of the filmstrip approximately 21/3 inches long, commonly referred to as a "film leader", protrudes from a light-trapped slit or mouth of the cassette shell. One end of the spool has a short axial extension which projects from the shell, enabling the spool to be turned by hand. If the spool is initially rotated in a film unwinding direction, the film roll inside the shell will tend to expand radially since the inner end of the filmstrip is attached to the spool, and the fogged leader section protruding from the slit will remain stationary. The film roll can expand radially until a non-slipping relation is established between its outermost convolution and the inner curved wall of the shell. Once this non-slipping relation exists, there is a binding effect between the film roll and the shell which prevents further rotation of the spool in the unwinding direction. Thus rotation of the spool in the unwinding direction cannot serve to advance the filmstrip out of the shell, and it is necessary to engage the protruding leader section to draw the filmstrip out of the shell.
If in the standard 35 mm film manufacturers' cassette, the film spool is rotated in a winding direction sufficiently to draw the protruding leader section of the filmstrip completely to within the cassette shell, it is very difficult to retrieve the leader section. U.S. Pat. No. 4,407,579, granted Oct. 4, 1983, appears to solve this problem by providing a film cassette wherein manual rotation of the spool in the unwinding direction can serve to advance the film leader out of the cassette shell. Specifically, the spool is comprised of two pieces constructed to telescopically receive one another. Each piece includes a radially extending flange which is adapted to lie closely adjacent to but not in engagement with one of the opposite sides of the film roll. A trailing end of the film roll is attached to the spool and a leading end of the roll rests against a cylindrical insert located between the two flanges and the cassette shell. The insert restricts the maximum diameter of the film roll to a value less than the diameter of the flanges and includes a slot leading to the light-trapped film passage opening of the cassette shell. To move the leading end of the film roll into the slot and through the light-trapped opening, to make it available outside of the film cassette, one must manually grasp the opposite ends of the spool and move the two pieces of the spool axially toward one another until the flanges are axially positioned in firm contact with the opposite sides of the film roll. While maintaining this inwardly directed manual pressure against the two pieces of the spool, one then must rotate the spool relative to the cassette shell in an unwinding direction. As a result, the leading end of the film roll will be rotated relative to the insert, causing it to be advanced into the slot of the insert and through the light-trapped opening of the cassette shell to the outside of the film cassette.
Although the film cassette disclosed in U.S. Pat. No. 4,407,579 includes an integral means whereby the leading end of the film roll may be retrieved from within the cassette shell, operation of that means is difficult because it requires a fair amount of manual dexterity. Moreover, since the operation must be performed manually it can only be accomplished prior to loading the film cassette into a camera.